Reversible total ionizing dose effects in NiO/Ga2O3 heterojunction rectifiers

Abstract

NiO/Ga2O3 heterojunction rectifiers were exposed to 1 Mrad fluences of Co-60 γ-rays either with or without reverse biases. While there is a small component of Compton electrons (600 keV), generated via the interaction of 1.17 and 1.33 MeV gamma photons with the semiconductor, which in turn can lead to displacement damage, most of the energy is lost to ionization. The effect of the exposure to radiation is a 1000× reduction in forward current and a 100× increase in reverse current in the rectifiers, which is independent of whether the devices were biased during this step. The on–off ratio is also reduced by almost five orders of magnitude. There is a slight reduction in carrier concentration in the Ga2O3 drift region, with an effective carrier removal rate of <4 cm−1. The changes in electrical characteristics are reversible by application of short forward current pulses during repeated measurement of the current–voltage characteristics at room temperature. There are no permanent total ionizing dose effects present in the rectifiers to 1 Mad fluences, which along with their resistance to displacement damage effects indicate that these devices may be well-suited to harsh terrestrial and space radiation applications if appropriate bias sequences are implemented to reverse the radiation-induced changes.

15 MeV proton damage in NiO/β-Ga2O3vertical rectifiers

“…The values obtained here for the NiO/Ga 2 O 3 , 1200 for 10 13 cm −2 and 190 cm −1 for 10 14 cm −2 are consistent with values reported for proton irradiation at similar energies/fluences but in Schottky diode structures that did not include the NiO [26,27]. This indicates that in contrast to gamma irradiation [29], the heterojunction rectifiers do not show any significant differences with the presence of the NiO for proton damage. The value determined at the higher fluence may already be in the saturation region where most of the carriers are already trapped at damage sites and therefore the value at low fluence is likely to be closer to the true number.…”

“…While the device performance is promising in terms of dc and switching applications [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], little is known about the effects of radiation on these heterojunctions. While the Ga 2 O 3 is known to be relatively resistant to total dose damage [27,28], large reversible changes in current-voltage characteristics of the heterojunctions have been observed after Co-60 gamma ray exposure which appears to be due to conductivity changes in the NiO [29]. Other low dose ion irradiated oxides have also shown enhanced conductivity which in some cases has been linked to irradiation/illumination assisted desorption of oxygen containing species from the oxide surface [30][31][32][33].…”

Forward bias annealing of proton radiation damage in NiO/Ga2O3 rectifiers

“…However, the implementation of p-type NiO to form heterojunctions with n-type Ga 2 O 3 has led to demonstrations of vertical rectifiers with excellent high-temperature operation [15][16][17][18][19][20][21][22][23][24][25]. The wide bandgap of Ga 2 O 3 means less charge is deposited during radiation exposure than for narrower gap materials and combined with the higher bond strength and high rate of dynamic annealing, indicates that Ga 2 O 3 may be well-suited to high radiation environments [26][27][28][29][30][31]. Ga 2 O 3 demonstrates notable resilience against total ionizing dose (TID) effects [27,28].…”